have virtio devices offer VIRTIO_F_ACCESS_PLATFORM if swiotlb

Have all virtio devices off VIRTIO_F_PLATFORM_ACCESS, which communicates
to the guest that DMA APIs should be used for allocating vrings and
virtio buffers. Since we have created a dedicated swiotlb region in the
geust and assigned all virtio devices to this, it means that all such
allocations will go through the swiotlb region.

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

src/vmm/src/builder.rs

@@ -605,6 +605,13 @@ fn attach_virtio_device<T: 'static + VirtioDevice + MutEventSubscriber + Debug>(
 ) -> Result<(), MmioError> {
     event_manager.add_subscriber(device.clone());
 
+    // We have to enable swiotlb as part of the boot process, because the device objects
+    // themselves are created when the corresponding PUT API calls are made, and at that
+    // point we don't know yet whether swiotlb should be enabled or not.
+    if vmm.vm.has_swiotlb() {
+        device.lock().unwrap().force_swiotlb();
+    }
+
     // The device mutex mustn't be locked here otherwise it will deadlock.
     let device = MmioTransport::new(vmm.vm.io_memory().clone(), device, is_vhost_user);
     vmm.mmio_device_manager

src/vmm/src/device_manager/mmio.rs

@@ -600,6 +600,10 @@ mod tests {
 
         fn set_acked_features(&mut self, _: u64) {}
 
+        fn force_swiotlb(&mut self) {
+            unimplemented!()
+        }
+
         fn device_type(&self) -> u32 {
             0
         }

src/vmm/src/devices/virtio/balloon/device.rs

@@ -25,7 +25,9 @@ use super::{
 };
 use crate::devices::virtio::balloon::BalloonError;
 use crate::devices::virtio::device::{IrqTrigger, IrqType};
-use crate::devices::virtio::generated::virtio_config::VIRTIO_F_VERSION_1;
+use crate::devices::virtio::generated::virtio_config::{
+    VIRTIO_F_ACCESS_PLATFORM, VIRTIO_F_VERSION_1,
+};
 use crate::logger::IncMetric;
 use crate::utils::u64_to_usize;
 use crate::vstate::memory::{Address, ByteValued, Bytes, GuestAddress, GuestMemoryMmap};
@@ -557,6 +559,10 @@ impl VirtioDevice for Balloon {
         self.acked_features = acked_features;
     }
 
+    fn force_swiotlb(&mut self) {
+        self.avail_features |= 1 << VIRTIO_F_ACCESS_PLATFORM;
+    }
+
     fn device_type(&self) -> u32 {
         TYPE_BALLOON
     }

src/vmm/src/devices/virtio/block/device.rs

@@ -148,6 +148,13 @@ impl VirtioDevice for Block {
         }
     }
 
+    fn force_swiotlb(&mut self) {
+        match self {
+            Block::Virtio(b) => b.force_swiotlb(),
+            Block::VhostUser(b) => b.force_swiotlb(),
+        }
+    }
+
     fn device_type(&self) -> u32 {
         TYPE_BLOCK
     }

src/vmm/src/devices/virtio/block/vhost_user/device.rs

@@ -16,7 +16,9 @@ use super::{NUM_QUEUES, QUEUE_SIZE, VhostUserBlockError};
 use crate::devices::virtio::block::CacheType;
 use crate::devices::virtio::device::{DeviceState, IrqTrigger, IrqType, VirtioDevice};
 use crate::devices::virtio::generated::virtio_blk::{VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_RO};
-use crate::devices::virtio::generated::virtio_config::VIRTIO_F_VERSION_1;
+use crate::devices::virtio::generated::virtio_config::{
+    VIRTIO_F_ACCESS_PLATFORM, VIRTIO_F_VERSION_1,
+};
 use crate::devices::virtio::generated::virtio_ring::VIRTIO_RING_F_EVENT_IDX;
 use crate::devices::virtio::queue::Queue;
 use crate::devices::virtio::vhost_user::{VhostUserHandleBackend, VhostUserHandleImpl};
@@ -294,6 +296,10 @@ impl<T: VhostUserHandleBackend + Send + 'static> VirtioDevice for VhostUserBlock
         self.acked_features = acked_features;
     }
 
+    fn force_swiotlb(&mut self) {
+        self.avail_features |= 1 << VIRTIO_F_ACCESS_PLATFORM;
+    }
+
     fn device_type(&self) -> u32 {
         TYPE_BLOCK
     }

src/vmm/src/devices/virtio/block/virtio/device.rs

@@ -27,7 +27,9 @@ use crate::devices::virtio::device::{DeviceState, IrqTrigger, IrqType, VirtioDev
 use crate::devices::virtio::generated::virtio_blk::{
     VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_RO, VIRTIO_BLK_ID_BYTES,
 };
-use crate::devices::virtio::generated::virtio_config::VIRTIO_F_VERSION_1;
+use crate::devices::virtio::generated::virtio_config::{
+    VIRTIO_F_ACCESS_PLATFORM, VIRTIO_F_VERSION_1,
+};
 use crate::devices::virtio::generated::virtio_ring::VIRTIO_RING_F_EVENT_IDX;
 use crate::devices::virtio::queue::Queue;
 use crate::devices::virtio::{ActivateError, TYPE_BLOCK};
@@ -578,6 +580,10 @@ impl VirtioDevice for VirtioBlock {
         self.acked_features = acked_features;
     }
 
+    fn force_swiotlb(&mut self) {
+        self.avail_features |= 1 << VIRTIO_F_ACCESS_PLATFORM;
+    }
+
     fn device_type(&self) -> u32 {
         TYPE_BLOCK
     }

src/vmm/src/devices/virtio/device.rs

@@ -102,6 +102,9 @@ pub trait VirtioDevice: AsAny + Send {
     /// - self.avail_features() & self.acked_features() = self.get_acked_features()
     fn set_acked_features(&mut self, acked_features: u64);
 
+    /// Make the virtio device offer the VIRTIO_F_ACCESS_PLATFORM feature
+    fn force_swiotlb(&mut self);
+
     /// Check if virtio device has negotiated given feature.
     fn has_feature(&self, feature: u64) -> bool {
         (self.acked_features() & (1 << feature)) != 0
@@ -259,6 +262,10 @@ pub(crate) mod tests {
             todo!()
         }
 
+        fn force_swiotlb(&mut self) {
+            unimplemented!()
+        }
+
         fn device_type(&self) -> u32 {
             todo!()
         }

src/vmm/src/devices/virtio/mmio.rs

@@ -423,6 +423,10 @@ pub(crate) mod tests {
             self.acked_features = acked_features;
         }
 
+        fn force_swiotlb(&mut self) {
+            unimplemented!()
+        }
+
         fn device_type(&self) -> u32 {
             123
         }

src/vmm/src/devices/virtio/net/device.rs

@@ -16,7 +16,9 @@ use vmm_sys_util::eventfd::EventFd;
 
 use super::NET_QUEUE_MAX_SIZE;
 use crate::devices::virtio::device::{DeviceState, IrqTrigger, IrqType, VirtioDevice};
-use crate::devices::virtio::generated::virtio_config::VIRTIO_F_VERSION_1;
+use crate::devices::virtio::generated::virtio_config::{
+    VIRTIO_F_ACCESS_PLATFORM, VIRTIO_F_VERSION_1,
+};
 use crate::devices::virtio::generated::virtio_net::{
     VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM, VIRTIO_NET_F_GUEST_TSO4, VIRTIO_NET_F_GUEST_TSO6,
     VIRTIO_NET_F_GUEST_UFO, VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_TSO6, VIRTIO_NET_F_HOST_UFO,
@@ -946,6 +948,10 @@ impl VirtioDevice for Net {
         self.acked_features = acked_features;
     }
 
+    fn force_swiotlb(&mut self) {
+        self.avail_features |= 1 << VIRTIO_F_ACCESS_PLATFORM;
+    }
+
     fn device_type(&self) -> u32 {
         TYPE_NET
     }

src/vmm/src/devices/virtio/rng/device.rs

@@ -13,7 +13,9 @@ use super::metrics::METRICS;
 use super::{RNG_NUM_QUEUES, RNG_QUEUE};
 use crate::devices::DeviceError;
 use crate::devices::virtio::device::{DeviceState, IrqTrigger, IrqType, VirtioDevice};
-use crate::devices::virtio::generated::virtio_config::VIRTIO_F_VERSION_1;
+use crate::devices::virtio::generated::virtio_config::{
+    VIRTIO_F_ACCESS_PLATFORM, VIRTIO_F_VERSION_1,
+};
 use crate::devices::virtio::iov_deque::IovDequeError;
 use crate::devices::virtio::iovec::IoVecBufferMut;
 use crate::devices::virtio::queue::{FIRECRACKER_MAX_QUEUE_SIZE, Queue};
@@ -303,6 +305,10 @@ impl VirtioDevice for Entropy {
         self.device_state = DeviceState::Activated(mem);
         Ok(())
     }
+
+    fn force_swiotlb(&mut self) {
+        self.avail_features |= 1 << VIRTIO_F_ACCESS_PLATFORM;
+    }
 }
 
 #[cfg(test)]